What is teleconference? And how does it differ from a regular telephone conversation (and even a conversation using Internet telephony)? There is a difference, and a significant one. It lies in the number of participants.
You've probably seen conference calls in the movies, and you may have participated in them yourself at work. If such meetings take place in the organization, a special apparatus is installed on the director's table, which allows choosing employees to participate in the conference. The employees themselves have ordinary telephone sets, sometimes not even equipped with dialers (instead of them there are plugs). Depending on the choice made by the director, each of the employees can either listen and speak, or just listen, or not participate in the meeting at all. This is also a kind of teleconference.
More sophisticated devices of this kind allow not only voice, but also video telephone communication. In some cases, this is very convenient: you can accompany the conversation by showing illustrations, fragments of drawings, diagrams, etc.
With the spread of the Internet, it became possible to use computers for teleconferencing. Initially, such conferences were only text-based. In particular, the IRC (Internet Relay Chat) protocol is designed specifically for their conduct, which allows you to create conferences in which a message sent by one participant is seen by all others. In the XMPP protocol, the capabilities of conference participants are expanded: they can not only communicate in text, but also draw explanatory diagrams on a common virtual board, and each line drawn by any of the participants becomes immediately visible to the rest.
Over time, software developers have made it possible to conduct virtual analogs of voice conference calls and video conferences on the Internet. To do this, you do not need to equip a computer with Internet access with any additional equipment, except for a camera and a microphone. Then everything happens in the same way as in ordinary IP-telephony, only there are not two participants, but more.
In some foreign countries, a user of an ordinary landline telephone can hold a teleconference by connecting a special conference call service. In Russia, a similar service is provided by cellular operators.
When talking with the use of walkie-talkies, the analogue of the teleconference is obtained automatically. The only difference is that the communication is not duplex but simplex. This means that you have to speak and listen in turn, but not at the same time.